The conventional power conversion systems for coupling renewable energy sources to utility grids have been Low-Voltage (LV) power conversion systems (<1000 V). However, particularly in the field of wind energy and for certain types of wind turbines, Medium-Voltage (MV) power conversion systems (>1000 V) would be desirable to improve its efficiency, because less current is needed to obtain the same power level.
The switching-frequency harmonic attenuation in power conversion systems is an important performance index in order to satisfy the standards of the IEEE 1547.2-2008 and 519-1992. In MV grid-tied inverters low switching frequencies (typically lower than 1.000 Hz) are required and said standards are more difficult to be satisfied than in LV grid-tied inverters.
The invention is addressed to the solution of this problem.